London, Aug 27 : Researchers in New York have discovered that a chemical can affect birds' singing, and thereby make them lose out on mates.
Sara DeLeon, an ecologist at Cornell University in Ithaca, came to this conclusion after studying wild chickadees exposed to polychlorinated biphenyls (PCBs), once used by power plants.
She found that birds exposed to the chemical, though look fit, but can't keep a tune as well as other birds.
"The birds are living, not dying, but [PCBs] are affecting some part of their life cycle," New Scientist quoted her, as saying.
Scientists have long known that some chemicals, such DDT, can throw off a bird's song, but none have determined whether exposure to trace amounts in the wild can influence songs and mating.
For the study, DeLeon and her colleagues examined chickadees living along New York's Hudson River, not far from a General Electric power plant that used PCB insulators from 1907 until the 1970s, dumping some 500,000 kilograms of the toxic chemical into the river.
Although numerous songbirds live along the Hudson, the researchers focused on black-capped chickadees, small birds with a two-note song. The best singers mix up the notes they sing, but the ratio between the two notes tends to stay the same.
On contrary, PCB-exposed birds sing all over the register. Birds that attempted to sing several different 'remixes' of the two-note song belted out songs with the notes too far apart. While birds that sing just one tune tend to blur the two notes together.
The researchers made the discovery after analysing the songs with a computer program. She said that the difference is only apparent to her when she can see the song as a visual spectrogram.
Tim DeVoogd, a neuroscientist also from Cornell, said the poorer vocal performances could arise because PCBs stunt growth and development in a part of the brain important for song.
"One of things they can do is mess up hormone receptors in the brain, and you need hormone receptors to develop correctly- to be either male-like or female-like. The birds might look like they are just fine, but they either can't produce a song or can't find a mate," he said.